1. Technical Field
Exemplary embodiments of the present invention relate to an image reader unit and an image forming apparatus including the image reader unit.
2. Background Art
Conventionally, a document or image reader unit as described below is known. The image reader unit includes a platen cover openably closable relative to a platen, and an optical mount including an LED array that includes a plurality of LED elements disposed in a main scanning direction along a surface of the document platen. The optical mount is movable along a surface of the platen in a sub-scanning direction perpendicular to the main scanning direction so as to optically scan an image on a document placed on the platen. The platen cover is closed by a user or operator relative to the platen, so that the document on the platen is pressed against the platen. In this state, the image reader unit, upon receipt of a reading start command from the user, causes the optical mount as a movable light emitter to radiate light beams from the plurality of LED elements toward a surface of the document, while receiving reflected light from the surface of the document, and to move in the sub-scanning direction. The image reader unit causes a charge-coupled device (CCD) used as an image sensor to receive the reflected light and scan the image of the document.
A processor of the image reader unit, before reading out the image of the document, performs processes to identify the length of the document in the main scanning direction. For this length identifying process, the image reader unit includes a sensor disposed near the platen cover to detect opening and closing of the platen cover. When the platen cover is opened to place a document on the platen, the sensor detects its opening operation. The processor of the image reader unit moves the optical mount from a predetermined standby position to a document size detection position opposed to a leading end of the document in the sub-scanning direction, upon the opening operation of the platen cover is detected. Thereafter, when the sensor detects a closing operation of the platen cover, the processor causes to perform the following length identifying process.
Specifically, among the plurality of LED elements included in the LED array, some of the LED elements necessary for identifying a length of the document in the main scanning direction alone is lit, and the reflected light obtained by the lighting is received by the CCD. Then, whether or not the document exists at a position opposed to each lit LED element is determined based on the received light quantity of an area opposed to each LED element in the light receiving area of the CCD in the main scanning direction, and the length of the document in the main scanning direction is identified based on the above determination result.